In the sci-fi book 'A deepness in the sky' by Vernor Vinge, zipheads are 'focused' persons in that they are utterly loyal and willing slaves whose attention can be focused on any facet of their personality to serve the needs of the controlling person. For example, a brilliant person can be turned into an utter genius. The ziphead will no longer have any free will and do not care, the slightest bit, about the things unrelated to what they were focussed into. They will become highly agitated and violent if not allowed to do what they were focussed to do.